The term ‘genetics’ conjures images of double helix DNA, lab coats and the study of inheritance. Nutrition and genetics are two things we generally don’t associate. However, the field of nutritional genomics has boomed over the past half-decade. Here’s what you need to know!
Nutritional genomics is a broad term that describes the relationship between many bioactive food constituents (those having an effect in the body through genes) and many physiological and biological processes. The study of nutritional genomics is so overwhelmingly complex, that to fully understand it, we must break it down into 3 smaller, easier to digest, subcategories. These are; nutritional epigenetics, nutrigenomics and nutrigenetics.
The most iconic example of nutritional epigenetics is the Dutch famine. The Dutch famine describes a cohort born in 1945-46 to pregnant women experiencing extreme famine during war time. The lack of nutrients received by the mother (and her baby), resulted in what we call a ‘thrifty metabolism’, where the body clutches scarce nutrients for dear life. Epigenetic modifications to DNA result in the development of such a metabolism where calories are stored and their breakdown is inhibited. Mother’s and babies within this cohort can thank their thrifty metabolism for their survival during the famine. However, the war ended, and the babies grew up. Dutch famine babies, now adults, have access to an abundance of food in our Western culture. A surplus of food and their thrifty metabolism (sustained through epigenetic tagging) is a deadly combination, resulting in a plethora of chronic diseases including type 2 diabetes, hypertension and coronary heart disease. Hence, unusually high prevalence of these diseases is observed in this unfortunate population.
It is examples like The Dutch Famine that make nutritional epigenetics, in my opinion, the most exciting area of nutritional genomics. This is because its’ effects are long term, sustained and can be inherited. Nutritional epigenetics has the potential to unleash better (or worse) health in a sustained manner that persists through generations. Like nutrigenomics, nutritional epigenetics describes how bioactive food constituents influence gene expression. Nutritional epigenetics, however, does not work using a transcription factor. Rather, the use of genome ‘tagging’ with chemical groups that influence gene expression. These tags are reflective of overall diet choices and can only be removed or attached with drastic, sustained lifestyle changes.
Nutrigenomics describes the phenomena whereby a bioactive food constituent can modulate gene expression through the action of a transcription factor. This is thought to, subsequently, increase the production of the protein that is coded by this gene.
It is helpful to understand nutrigenomics in the context of an example. Hydroxytyrosol is a bioactive food constituent found in olive oil. Cell studies have shown hydroxytyrsol to have a signalling effect which causes the movement of its transcription factor to the nucleus. Once in the nucleus, the transcription factor binds to specific regions of DNA and up regulates the expression of antioxidant and detoxification enzymes. Hence, it would be expected to see an increase in antioxidant and detoxification capabilities of the cell. However, it’s not always that simple. Just because studies have been shown successful in cells, this does not necessarily mean they accurately translate to activity in the human body. There is still so much we don’t know!
Another important thing to understand about nutrigenomics is that the response is acute. This means that the relevant genes are only modulated for as long as the exposure and frequent consumption of bioactive nutrients is imperative for a nutrigenomic effect. If it’s a more sustained effect you’re after, then nutritional epigenetics is for you!
Nutrigentics works in the opposite direction to nutritgenomics and nutritional epigenetics. It is how the genes influence an individual’s response to food.
My mum always told me ‘everyone is special’, and she was right! Everyone has their own unique genetic code with various mutations and epigenetic tags. This is what makes you, you. It is also why your friend can handle ice cream, milk and cheese with no problem, while you get bloating, cramps and diarrhoea.
Lactase is the enzyme that metabolises dairy sugar. It is coded by a set of genes that are ‘turned off’ in some people, but ‘turned on’ in others. Those with the ‘turned on’ lactase genes are called lactase persistent and can enjoy delicious dairy delicacies with no problems at all. Meanwhile, their ‘turned off’ counterparts experience discomfort. This is one example of nutrigenetics.
More concerning than just a bit of bloating, is how individuals might response to differently to ‘healthy’ nutrients. What is healthy for one, might not be healthy for another. For example, polyunsaturated fatty acids are promoted as healthful nutrients that combat heart disease. However, some studies have shown them to exacerbate hypertension in individuals with a specific genotype. Hence, it is necessary to understand the personalised genetic makeup before we administer dietary advice. The problem is, mapping a genome is no easy feat. Nor is it cheap. Furthermore, we are yet to fully understand all the thousands of possible genetic mutations that influence how we respond to food. Therefore, we are still a long way off being able to apply the principle of nutrigenetics in practice.
In conclusion, nutritional genomics encompasses nutrigenomics, nutritional epigenetics and nutrigenetics. It’s not just distinguishing the difference between these frustratingly similar-sounding terms that makes nutritional genomics so complex. We are only just beginning to uncover the tip of the iceberg in this field, with new genetic variants and nutrient interactions being discovered all the time. For this reason, it is important apply the principles of nutritional genomics with extreme caution. Never the less, genetic studies are likely to shape the future of clinical dietetics and provide a helpful tool for achieving truly personalised nutrition interventions.